当前我国隧道工程建设正往长距离、超深埋深、大断面等方向发展，地质环境往往趋于复杂，由于山区高地应力、围岩破碎、地下水丰富等因素，使得隧道施工过程中常常面临非对称大变形问题。了解岩体层状结构的受力和变形特征及高地应力对围岩变形的影响机制对于确定支护设计和施工方案具有重要的指导意义。文章以渭武高速公路木寨岭隧道为工程背景，从现场典型层状围岩变形特征出发，运用文献调研、现场监测、室内试验和数值模拟等方法，对极高地应力层状软岩隧道非对称大变形特征进行了深入研究，主要研究工作及结论如下：

（1）对木寨岭隧道地质勘察报告进行梳理，进行了现场典型层状围岩断面的变形监测以及统计调研了相关层状软岩隧道围岩变形资料。结果表明：木寨岭隧道区域强度应力比小于4，属于极高地应力区；隧道围岩变形呈明显非对称现象；隧道围岩非对称大变形变形的主要影响因素为岩体软硬程度、地下水赋存、最大主应力大小、岩层产状（倾向、倾角）等。

（2）开展了不同层理倾角的层状板岩常规单、三轴压缩试验，分析层状板岩的各向异性力学特性。结果表明：随层理倾角增大，试样的纵波波速、内摩擦角及弹性模量逐渐增大；抗压强度及粘聚力呈先减小后增大的“U”型特征。同一层理倾角下，试样抗压强度和弹性模量与围压成正比。层状板岩试样破坏模式受层理弱面控制，按层理倾角分为，0°时穿越层理面的剪切破坏、倾斜层理时的剪切滑移破坏及90°时沿层理面的张拉劈裂破坏。基于横观各向同性理论计算了层状板岩压缩过程中的特征应力，得到60°倾角试样极易发生沿层理面的剪切滑移破坏。

（3）通过数值模拟，开展了层状软岩隧道非对称大变形影响因素研究，结果表明：① 随着层理倾向、倾角的改变，围岩位移云图形态发生偏转，表现出明显的差异性，围岩的最大变形位置始终发生在垂直层理面方向上。② 随水平侧压力系数的增加，倾斜层理的错动现象趋于明显，隧道洞周水平收敛位移逐渐增大并大于拱顶下沉位移。③ 随平行和垂直层理面弹性模量的增加，围岩变形量值呈线性减小，且隧道洞周围岩变形增幅受层理倾角控制。

（4）对围岩塑性区的研究结果表明：① 层理产状改变，塑性区主方向发生偏转，但最大塑性区位置始终在垂直层理面方向上；最大塑性区深度随倾角增大先增大后减小，在30°时塑性区深度最大；随层理倾向增加塑性区逐渐增大。② 随侧压力系数增大，塑性区的深度及范围将会增加，对倾斜层理影响更为显著，在垂直层理面方向上形成一条狭长的剪切破坏区。③ 平行和垂直层理面弹性模量对塑性区影响较小，与最大塑性区深度及范围成反比。

（5）借助数值模拟，对上述高地应力层状软岩隧道的大变形影响因素开展正交试验。结果表明：围岩最大变形值及最大塑性区深度的影响优先级为层理面倾角＞层理面倾向＞水平侧压力系数＞垂直层理面的弹性模量＞平行层理面的弹性模量。

Due to the characteristics of high geostress, layered rock mass fragmentation and groundwater abundance in mountainous areas, the construction process often faces the problem of asymmetric large deformation, and it is of guiding significance to accurately understand the influence mechanism of layered rock mass structure and high geostress on the deformation of surrounding rock. Based on the research background of the Muzhailing tunnel project of Weiwu Expressway, starting from the deformation characteristics of typical layered soft surrounding rock in the site, this paper mainly uses literature investigation, field monitoring, indoor mechanical test and numerical simulation to conduct an in-depth study on the asymmetric and large deformation characteristics of extremely high-stress layered soft rock tunnels, and the main research work and conclusions are as follows:

(1) The geological survey report of the Muzhailing tunnel was combed, the deformation monitoring of the typical layered surrounding rock section on the site was carried out, and the deformation data of the surrounding rock of the relevant layered soft rock tunnel were statistically investigated. The results show that the strength-stress ratio of the Muzhailing tunnel area is less than 4, which belongs to the extremely high geostress area. The deformation of the surrounding rock of the tunnel is obviously asymmetrical. The main influencing factors of asymmetric large deformation of the surrounding rock of the tunnel are the softness and hardness of the rock mass, the occurrence of groundwater, the magnitude of the maximum principal stress, and the occurrence (d-d, dip), etc.

(2) Conventional uniaxial and triaxial compression tests of layered slate with different bedding dip angles were carried out to analyze the anisotropic mechanical properties of layered slate. The results show that with the increase of bedding inclination, the longitudinal wave velocity, internal friction angle and elastic modulus of the sample increase gradually. The compressive strength and cohesion are "U" shaped characteristics, which decrease first and then increase. Under the same bedding inclination, the compressive strength and elastic modulus of the specimen are proportional to the confining pressure. The failure mode of layered slate specimens is controlled by the bedding weak surface, which can be divided into shear failure through the bedding plane at 0°, shear slip failure at inclined bedding and tensile splitting failure along the bedding plane at 90°. Based on the transverse isotropic theory, the characteristic stresses of layered slate during compression are calculated, and it is obtained that the samples with a 60° inclination angle are very prone to shear slip failure along the bedding plane.

(3) The results show that:① With the change of bedding tendency and dip angle, the shape of the displacement cloud map of the surrounding rock is deflected, showing obvious differences, and the maximum deformation position of the surrounding rock always occurs in the direction of the vertical bedding plane.② With the increase of the horizontal side pressure coefficient, the dislocation phenomenon of inclined bedding tends to be obvious, and the horizontal convergence displacement around the tunnel gradually increases and is greater than the sinking displacement of the vault.③ With the increase of the elastic modulus of the parallel and perpendicular bedding planes, the deformation of the surrounding rock decreases linearly, and the deformation amplitude of the surrounding rock is controlled by the bedding dip angle.

(4) The results of the study of the plastic zone of the surrounding rock show that:① the occurrence of the bedding changes, and the main direction of the plastic zone is deflected, but the position of the maximum plastic zone is always in the direction of the vertical bedding plane; The maximum depth of the plastic zone increases first and then decreases with the increase of inclination angle, and the maximum depth of the plastic zone is at 30°. With the increase of bedding tendency, the plastic zone gradually increases.② With the increase of lateral pressure coefficient, the depth and range of the plastic zone will increase, which will have a more significant impact on the inclined bedding, and a narrow shear failure zone will be formed in the direction of the vertical bedding plane.③ The elastic modulus of parallel and perpendicular bedding planes has little influence on the plastic zone, which is inversely proportional to the depth and range of the maximum plastic zone.

(5) With the help of numerical simulation, orthogonal tests were carried out on the influencing factors of large deformation of the above-mentioned high geostress layered soft rock tunnels. The results show that the influence of the maximum deformation value of the surrounding rock and the depth of the maximum plastic zone are the dip angle of the bedding plane> the tendency of the bedding plane> the horizontal lateral pressure coefficient> the elastic modulus of the vertical bedding plane> the elastic modulus of the parallel bedding plane.